Lithium Nuclear Spin Polarization Lifetimes as Sensitive Reporters of Battery Electrolyte Degradation

Nondestructive monitoring of electrolyte degradation is a critical, yet unresolved challenge in the diagnostics of lithium-ion batteries. Here, we report the potential utility of nuclear spin polarization lifetime T₁ as a highly sensitive, intrinsic probe for monitoring the health of a model LP30 electrolyte under thermal cycling by using multinuclear NMR spectroscopy. We identified a particularly sensitive correlation between the degradation state and ⁷Li relaxation dynamics that is not observed for other relevant nuclei. Molecular dynamics simulations provide a mechanistic rationale, linking the observed relaxation changes to specific alterations in the Li-ion solvation shell structure during the degradation. These findings establish ⁷Li spin lifetime as a robust, field-independent analytical metric, with potential application to the noninvasive assessment of battery state-of-health in regimes where chemical shift resolution is insufficient for species discrimination.